Hipparcos-Gaia PMA sensitivity to companions of a given mass (in M_⊕) as a function of the orbital semi-major axis (in AU) orbiting Barnard’s star. The solid black line identifies the combinations of mass and separation explaining the observed proper-motion anomaly (PMA) at the mean epoch of Gaia DR3 (Eq. (15) in Kervella et al. 2019). The shaded light-blue region corresponds to the 1σ uncertainty region.